Power-factor indicator.



J. R. GRA'IGHEAD.

POWER PASTOR INDICATOR.

APPLICATION TILED OCT. 7, 1911.

Patented June 10, 1913.

[r2 ventor James P. Cra g/wad, wax/M114 QW' M's'flttor'ne g.

Witnesses:

ill ll'fl ltl STATES iliATENT l l litflll,

JAME GRAIGHEAD, OF SCHENECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY. A CORPORATION OF NEW YORK.

POWER-FACTOR INDICATOR.

Specification of Letters Patent.

Patented June ll, illiit.

Application filed flctobei' 7, 1911. Serial No. 653,389.

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lie it known that l Janus It. 3R.\1(l!U-l.\l), a. citizen of the United States, residing at Schenectady, county of Schenectady, State ot New York, have 1nvented certain new and useful improvements in lmver-lhctor In dixators, of which the following is a spec fication.

My invention relates to devices for indicating the power factor of alternating current circuits, and its object is to provide a simple and cllieicnt power factor indicator which not a'ti'ectcd by ordinary changes in frequency occurring in conunereial circuits.- i obtain the desired result by pro iding two relatively movable elements, each uiluding two or mrre i'nechanically dispaced windings, employed phase splitting n1 ans in circuit with the windings of each cl merit, so as to hroduce in each element a. rotating tic d. and giving to the phase s ditting means for each element such char-- .lcleristics that the circuits of that element hare the same time constants as those of the other element. With such an arrangement a change in frequency which changes the phase of the currents in the windings of either rlenient produces a precisely similar change in the windings of the other elemcnt', so that the indication of the instrumcat is not ailectcd by the ordinary variations of tl'rcquency in commercial circuits.

My invention will best be understood by reference to the accompanving drawings, in which-- cl igurc 1 shows diagrannnatically a power factor indicator arranged in accordance with 111) invention, ud Fig. 9 shows a moditicaticn in the circuit cminections.

in l iu'. l A and A represent two coils or windiir which constitute the stationary element of the instrument: It only two windings are employed. they are preferably 'dis )laced from each other by 90 de rees as shown. The i'novingr clement comprises two similar coils ll and B. The coils A and A are connecti-ul in parallel, with impedances o and (1, included in the parallel circuits iii series with the two coils, respectively. These two impedances are of ditt'erenl time constants. so as to produce a phase displacement between the currents in the two coils A and A. The. impedance a is represented as a reactance and ti as a non-imluctive resistance. The coils A and A, with their impedauces, are connected in series with the circuit C, the power factor of which is to be measured. The alternating generator for the circuit is indicated diatrrainmatimiily at D. The coils A and A thus constitute the current coils of the instrument. The movable coils l3 and ll are the potential coils. These also are connected in parallel, with impcdances I) and Z) ol' dillrrent time constants incuu'led in. the parallel circuits. The coils B it, with their iiupfllances, are connected in shunt to the circuit t. through a noirinductive resistance 0 ol' sullicieut amount to make the current llowlngr through it. andL consequently the resultant current of the coils B and it. substantially in phase with the voltage in circuit (l. The moving; element of the instriuneut rarrics a suitable pointer it, moving over a suitable scale I. lVhen the current in the circuit (1 is in phase with the Volta re. the re.--:ultant of the current in coils A and will he in phase with the resultant ol. the current in coils B and B. Furtllermore. it the time constant of the circuit of impedance 1) is the same as that of o and the time constant of the circuit oi. impedance .6 is the same as that of impedance o, and it the ratio of impedance between a and i) is the same as that between a, and 7), the current in coil B will be in phase with the current. in coil A and the current in coil 13 will be in phase with the current in coil A; and also tin atios of the currents in coils A'and B and l. coils A. and B will be the same. Under ese conditions the movable element will occt vy the position shown, with each of the 1m able coils parallel with the correspondiru stationary coil. The best condition for minimum error in the readings of the instriuntat due to commercial changes of frequency is, obviously. obtained when the resistance of circuit B equals the impedance of circuit B and the resistance of circuit A equals the impedance oft circuit A at the rated frequency of the instrument. It the current in circuit C is not in phase with the voltage of the circuit, the currents in the stationary and movable elements will not be in phase, but will be displaced l an amount corresponding to the displacen'lent of the currentin circuit/C from the voltage. The movable element of the instrument will consequently stand at an angle from that shown in the drawings, the amount of the lift aft

is produced in the coils of one element there will be a co p ling change in the currents in thecoils he other element because the circuits ie two elements have the same time constants and proportional impedances, so that an increase in frequency, for instance, which would produce a greater lag" of the current in coil A with respect to the current in circuit C will produce a precisely similar increase of lag in coil B with respect to the voltage of circuit C, so that the re tive phases of current in coils .l-a and B will not be altered.

2 modification of the circuit shown. In this figure the with heir impedances, in- "ed directly in the circuit as a non-inductive ree s with the circuit. EVi'th neat the voltage impressed on I is in phase with rent, and it consequentlybecomes unnecessary to employ in the circuit-of coils" B and B the non-inductive resistance shown at c in 1, since if the time constants of the circuits of the stationa y and movable elements the same the! the currents the coils of the two eleme s will be in when the current of circuit C is in 1 2B voltage, because then the circuits of the stationary and movable er are in phase.

I not desiii': to limit myself to the particular construction and arrangement of parts shown and described, but aim in the appended claims to cover all modifications which are within the scope of my invention.

What if claim as new and desire to secure oy Let atent of the United States, is,

l, factor meter comprising relatively moi pan displacements of the currents therein, the

time constantof the circuit of each impedance and the winding of one element 1n cuit with the different windings of either element having different time constants and producing phase displacement of the currents in the windings of that element but each circuit for one element having the same time constant as a corresponding circuit for the other element, and indicating means actuated by the movable elcment'of the meter.

4. A power factor meter comprising relatively movable elements, each including a plurality of mechanically displaced windings connected in pa *allcl circuits, the parallel circuits for the different windings of either element having different time constants but each circuit for one element having the same time constant acorresponding circuit for the other element, andindicating means actuated by the movable element of the meter.

5. A power factor meter comprising relatively movable elements, each including a plurality of mechanically displaced wihdings, phase splitting means in circuit with the windings of each element, the circuits for each element having the same time constants as the corresponding circuits of the other element and the amount of the inn pedance of the inductive circuit of each element being approximately e. ...i.l. to the resistance of the non-inductive circuit of the same element at the rated frequency of the instrument, and indicating means actuated by the movable element of the meter.

6. A power factor meter comprising relatively movable elements, each including a plurality of mechanicallydisplaced windings, phase splitting means in circuit with the windings of each element. the circuits for each element having the same time constunts as the corresponding circuits of the other element and the amounts of the impedances of two circuits of one element having the same ratio to each other as those of the other element, and indicating means actuated by the movable element of the meter.

In witness whereof, I have hereunto set my hand this 6th day of October, 1911.

JAMES R. CRAIGHEAD.

Witnesses:

BENJAMIN l3. H LL, HELEN Onronn.

It is hereby certified that in Letters Patent No. 1,064,131, grant-ed June 10,

1913 upon the application of James R. Craighead, of Schenectady, New York, for

an improvement in Power-Factor Indicators, an error appears in the printed specification requiring correction as follows: Page 1, line 18, for the word employed read employing; and that the said Letters Patent should be read with this correction therein thetthe same may conform to the record of the ease in the Patent Ofiice.

Signed and sealed this 8th day of July, A. D., 1913.

[SEAL] C. O. BILLINGS,

Actn g Commissioner of Patents. 

